Invocation of method 'getSession' in class org.apache.catalina.connector.RequestFacade threw exception java.lang.IllegalStateException: Cannot create a session after the response has been committed at /layout/2019/_header.vm[line 8, column 24]

java.lang.IllegalStateException: Cannot create a session after the response has been committed
at org.apache.catalina.connector.Request.doGetSession(Request.java:2944)
at org.apache.catalina.connector.Request.getSession(Request.java:2314)
at org.apache.catalina.connector.RequestFacade.getSession(RequestFacade.java:895)
at org.apache.catalina.connector.RequestFacade.getSession(RequestFacade.java:907)
at sun.reflect.GeneratedMethodAccessor133.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.doInvoke(UberspectImpl.java:395)
at org.apache.velocity.util.introspection.UberspectImpl$VelMethodImpl.invoke(UberspectImpl.java:384)
at org.apache.velocity.runtime.parser.node.ASTMethod.execute(ASTMethod.java:173)
at org.apache.velocity.runtime.parser.node.ASTReference.execute(ASTReference.java:280)
at org.apache.velocity.runtime.parser.node.ASTReference.evaluate(ASTReference.java:530)
at org.apache.velocity.runtime.parser.node.ASTNotNode.evaluate(ASTNotNode.java:63)
at org.apache.velocity.runtime.parser.node.ASTAndNode.evaluate(ASTAndNode.java:104)
at org.apache.velocity.runtime.parser.node.ASTExpression.evaluate(ASTExpression.java:62)
at org.apache.velocity.runtime.parser.node.ASTIfStatement.render(ASTIfStatement.java:85)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342)
at org.apache.velocity.runtime.directive.Parse.render(Parse.java:260)
at org.apache.velocity.runtime.parser.node.ASTDirective.render(ASTDirective.java:207)
at org.apache.velocity.runtime.parser.node.SimpleNode.render(SimpleNode.java:342)
at org.apache.velocity.Template.merge(Template.java:356)
at org.apache.velocity.Template.merge(Template.java:260)
at org.apache.velocity.tools.view.VelocityView.performMerge(VelocityView.java:942)
at org.apache.velocity.tools.view.VelocityView.merge(VelocityView.java:902)
at org.apache.velocity.tools.view.VelocityViewServlet.mergeTemplate(VelocityViewServlet.java:318)
at org.apache.velocity.tools.view.VelocityLayoutServlet.mergeTemplate(VelocityLayoutServlet.java:247)
at org.apache.velocity.tools.view.VelocityViewServlet.doRequest(VelocityViewServlet.java:220)
at org.apache.velocity.tools.view.VelocityViewServlet.doGet(VelocityViewServlet.java:182)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:622)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:292)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:240)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:207)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:212)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:94)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:141)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:509)
at org.apache.coyote.ajp.AbstractAjpProcessor.process(AbstractAjpProcessor.java:877)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:684)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1524)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1480)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:745)